


come undone now

by starboykeith



Series: SHEITH MONTH 2017 [1]
Category: Voltron: Legendary Defender
Genre: Aftercare, Anal Fingering, Anal Sex, BDSM, Bottom Keith (Voltron), Colour System, Consent, Established Relationship, Keith Calling Shiro Sir, M/M, Orgasm Delay, Praise Kink, Safewords, Sheith Month 2017, Spanking
Language: English
Status: Completed
Published: 2017-08-01
Updated: 2017-08-01
Packaged: 2018-12-01 21:39:32
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,863
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/11495277
Author URL: https://archiveofourown.org/users/starboykeith/pseuds/starboykeith
Summary: Keithknowswhat it does to Shiro when he letssirslip - because he has an unfortunate habit of promptly saying, "Yes, sir," when Shiro gives him an order, whether they're being intimate or not - but today he was doing it on purpose.And cadets who misbehave get punished.





	come undone now

**Author's Note:**

> for the prompt "yes, sir" for day one of sheith month 2017
> 
> what a way to kick off the month :^) i clearly went for the worst interpretation possible
> 
> title is from design by tender

Keith was being mouthy again.   
  
He _knows_  what it does to Shiro when he lets _sir_  slip - because Keith has an unfortunate habit of promptly saying, "Yes, sir," when Shiro gives him an order, whether they're being intimate or not - but today he was doing it on purpose.   
  
Shiro had been glad they were training in lions only - because it hid that he was getting _hard_ , biting his lip and shifting uncomfortably every time Keith called him 'sir' - and Shiro knew it wasn't an accident because Keith made sure to curl his tongue around the words, dripping with honey and promising that he knew exactly what he was doing.   
  
And cadets who misbehave get punished.   
  
Shiro has him up against the wall as soon as they reach his room, sparing a thought to lock the door behind them but mostly focusing on pinning Keith with his weight. Pinning Keith's wrists comes just after, and is hardly necessary, because Keith's breathing sharp and fast the way he does when he _wants_  it, and he wouldn't squirm away now.   
  
Keith tries to kiss him, but Shiro leans just out of reach, smirking at the little frustrated noise that escapes Keith's mouth.   
  
Instead, he tips Keith's chin up with one finger, higher and higher until Keith breathes out in a shaky exhale.   
  
"What's your safeword, cadet?" he asks softly, and has the pleasure of watching Keith's pupils dilate, his cheeks flush.   
  
"Voltron," Keith says, and he inhales sharply when Shiro drops his hand.   
  
"Voltron..." Shiro prompts, and Keith squirms under his gaze.   
  
"Voltron, sir," he whispers.   
  
"Good," Shiro says, and he does kiss Keith then, short and sweet on the lips, before pulling away, letting Keith stand on his own. "You're going to strip for me," he says, while Keith's still swaying a little. "And then you're going to get into position on the bed."   
  
"Yes, sir," Keith breathes, and he starts right away, because he _can_  be good, so good, sometimes.   
  
Shiro circles him as he strips swiftly out of uniform trousers, shirt, boxers; kicking away his socks. Keith's blush is spreading down his chest.   
  
"Colour?" Shiro asks.   
  
"Green."   
  
Keith gets on the bed and on all fours. He doesn't lean his head on his forearms just yet, but he will, Shiro thinks, watching Keith arch his back higher and spread his legs wide.   
  
He hears Keith's sharp inhale when he puts one knee on the bed and smirks, because Keith might misbehave but Shiro knows he can be good, really.   
  
"Good," he says, because his baby loves to hear it out loud. He strokes his metal hand down the arch of Keith's spine and Keith shivers for him.   
  
And then he waits.   
  
Keith doesn't move at first - twitches idly, shifts his hands and feet, cock already heavy and flushed between his legs - but as time goes by his breathing picks up just a little and he turns his head just slightly -   
  
He gasps when Shiro smacks his thigh, only a light tap but getting the message across, and he hangs his head again, waiting, now.   
  
"You've been very bad," Shiro says slowly, caressing the place he'd hit, the skin there flushing pink. "Do you know what you did?"   
  
"Yes, sir."   
  
"And what did you do?"   
  
"I was trying to," Keith's huffing, embarrassed, "I was trying to - rile you up." He pauses. "Sir."   
  
"Mm," Shiro hums. "I think you deserve a spanking."   
  
Keith breathes in sharply, but doesn't respond. Shiro pets the swell of his ass fondly.   
  
"Do you agree?"   
  
" _Yes_ , sir," Keith says fervently, the words spilling like he'd been waiting for Shiro to ask.   
  
Shiro gets off the bed to fetch the lube out of the bedside drawer, feeling Keith's eyes on him. He's still clothed, but that will have to do right now, because _someone's_  pretty ass needs a spanking and Shiro's all out of patience.   
  
"Colour?" he asks while his back is turned.   
  
"Green, sir."   
  
When he returns to Keith, Shiro spends some time just touching him - running hands over his waist; rubbing at the firmness of Keith's ass; spreading him and dipping inward to thumb at his hole. Keith tries to stay quiet, he really does, and the effort is what makes Shiro forgiving.   
  
"You're going to count for me," Shiro says finally, and without waiting for a response he gives the flesh a hard smack that makes it _bounce_.   
  
"One," Keith says, and he's breathless already. He isn't going to last long, Shiro thinks, and it brings a smirk to his lips, but -   
  
"One, what?" he asks dangerously, voice thin like a knife's edge.   
  
He doesn't know if Keith genuinely forgot, or if he likes the thrill, but he smacks Keith's ass again anyway, relishing Keith's little gasp.   
  
"One, sir!"   
  
"Good boy," Shiro says, and Keith's knees move a little further apart in the sheets.   
  
Keith remembers every time after that, but he's being a little reticent, Shiro thinks, imagining Keith biting his lips to keep back his noises. It always takes some time to get Keith to make noise, but Shiro is patient.   
  
On the fifth smack, Keith cries out in earnest, and it sounds like a real release, as though Keith's been trying so hard to hold back and finally couldn't anymore. His thighs are tense with trying to keep still, forehead pressed against his forearms and meaning Shiro can't see that pretty face when Keith makes a sound like a sob.   
  
"Six, sir," he pants.   
  
"Colour?" Shiro asks, because he knows it can be too much for Keith sometimes.   
  
"Amber," gasps Keith, and he's trembling a little. "I can't - not much longer, or I'll - "   
  
"You'll come when I tell you to," Shiro says automatically, but he brushes his hand over Keith's thigh, soothing. "How many more can you take?"   
  
"Four more, please, sir," Keith says, and Shiro's pleased and proud that his boy knows his limits and to ask for what he wants.   
  
When he smacks Keith's ass this time, it earns him a breathy little, "Ah!" noise that goes straight to his cock, makes him think about Keith sitting down on it, ass red and raw from spanking and yeah, Shiro thinks, they're doing that today. He palms himself to relieve some of the pressure, and returns his attention to where it's needed most.   
  
Keith gets louder and louder until he _sobs_  with, "Ten, sir!" and Shiro tells him to relax, watching Keith's knees slip out from under him as he presses the side of his face to the cool pillow.   
  
"Colour?" he asks anxiously, because Keith isn't normally so - affected.   
  
"Green, sir," says Keith, and after a moment he gets back into position all on his own.   
  
"Good; good boy," Shiro says, and when he runs his hand down Keith's spine Keith arches into it like a cat, moaning softly when Shiro's hand moves to his ass, to the skin reddening gorgeously under his fingers.   
  
He's uncomfortably aware this turned from punishment to their usual arrangement where Shiro can't get enough of taking care of Keith, so he says, "Have you learned your lesson?"   
  
There's a smile in Keith's voice when he replies, "I think so, sir."   
  
"You think so?" Shiro hums, considering. "Well, I better make sure it gets into you somehow." The pun brings a reluctant smile to his lips and reminds him, however tough he's pretending to be, he's still ridiculously stupid over Keith.   
  
"And how will you do that, sir?"   
  
Even when Keith is an insolent little brat.   
  
Shiro pretends to think. "Well," he says. "I think I'm going to open you up on my fingers and fuck you till you cry."   
  
That shuts Keith right up, Shiro thinks, smirking as Keith visibly squirms and takes a deep breath.   
  
"Green, sir," he says without being prompted. He darts a glance back at Shiro when Shiro starts taking his clothes off, tossing them without care to the floor, but Shiro doesn't pick him up on it, just smirks and lets him look.   
  
When he gets back on the bed, he taps Keith's thigh with one finger and says, "Turn over."   
  
Keith rushes to comply, thighs falling open as he rolls onto his back, and Shiro smiles when he sees Keith's eyes are wide and dark.   
  
He _could_  tease Keith, could fuck him on his fingers until he's trembling and flushed and squirming - and Shiro does so love Keith writhing on his fingers - but Shiro's been thinking of nothing all day but fucking Keith, ever since the first smarmy, "Yes, _sir_ ," left Keith's mouth that morning.   
  
Keith moans when Shiro starts rubbing at his hole, and as Shiro watches his fingers curl into the sheets he gets an idea.   
  
"Hold your legs up for me," he says, and Keith flushes, undoubtedly feeling exposed as he grips his knees and holds them in the air, revealing himself to Shiro's hungry gaze.   
  
"You look so good, baby," Shiro whispers, and he gets lube on his fingers and pushes one inside, watching Keith's head tip back in the pillow.   
  
"Th-thank you, sir," Keith says breathily, stuttering because Shiro adds another finger and starts stretching him properly, and Keith's toes curl, his face scrunching up in that way he does when it's almost too much, _too_  good.   
  
Shiro loves that face.   
  
"Colour?" he asks, eyes on the way Keith's hole stretches around his fingers. The redness painting the very tops of his thighs is faintly visible, and Shiro strokes the skin there with his metal hand and watches Keith tremble.   
  
"Green, sir," Keith says.   
  
Shiro fingers him like that until Keith really is squirming, face red and breathing hard, and Shiro can tell he wants to ask for another and knows he shouldn't.   
  
"Good," Shiro says, and when he slides in his third finger, Keith actually moans in relief. "You're doing so good, Keith."   
  
He thinks Keith might reply to that one too, but all Keith can manage is a muffled, "Mmm," his hands sliding on his knees with sweat as he holds them up for Shiro, straining with the effort.   
  
Shiro doesn't draw it out much longer, because _he_  wants it, too, and much as he loves driving Keith to the edge like this, just on his fingers, Keith deserves something for being so good.   
  
Keith moans again when Shiro withdraws his fingers, and Shiro admires the way his hole flutters, trying to clamp down on nothing after being so full, gaze moving back to Keith's face just as Keith stops biting his lip.   
  
Shiro can't resist moving back to bite Keith's reddened swollen lips for himself, and Keith surges into it, letting go of his legs and letting them fall splayed in the sheets as he kisses back hard and desperate, gasping when Shiro pulls back for breath.   
  
"Sir," Keith says quietly, and Shiro knows what he wants.   
  
"You know you can ask me for anything you want, baby," he says, running his metal fingers up Keith's side to make him squirm. Keith's ticklish and hates it, but he loves it when they're like this.   
  
"Please fuck me, sir," Keith says breathlessly, and _fuck_ , Shiro knew it was coming but it still takes his breath away, his baby underneath him and begging to be fucked. "Please, sir," Keith continues, clearly taking Shiro's silence as a rejection, or a tease, and Shiro knows Keith still finds dirty talk hard so he waits as Keith finds the words. "I - I want you inside me, I want to sit in your lap and - and - "   
  
"You want to sit down on it?" Shiro asks, and Keith blushes and nods. "Come on then, sweetheart." Keith looks at him sharply, and Shiro sits back and gets himself comfortable on his knees, watching Keith's gaze lower to his cock, hard and flushed against his belly, as he rolls a condom on and strokes himself with lube to make it easier, because he wants Keith to be _easy_.   
  
Keith crawls over to him - and isn't _that_  something - and then he turns and squirms backwards a little, and Shiro takes Keith's waist in his hands and _lifts_  him, settling Keith in his lap, cock just brushing where Keith's wet and open for him. Keith's legs are spread so wide, hooked over Shiro's like this, and his chest is heaving under Shiro's hands.   
  
"Go on, baby," Shiro says, and Keith's hands fall hard on his knees when Shiro lets go, letting Keith start sitting down, and the hot, tight heat makes him groan, hands fisting in the sheets in an effort to stay still as Keith takes all of him inside and hangs his head forward, panting.   
  
"Colour?" Shiro asks softly, and he shifts them so he's got an arm around Keith's waist, giving him the leverage he wants.   
  
"Green," Keith breathes, and when he exhales, all the tension in his body goes with it until he's leaning most of his weight on Shiro, powerless and submissive.   
  
"Good boy," Shiro murmurs, and then he's had enough of being gentle.   
  
Even just the first thrust makes Keith cry out, and Shiro keeps going, starts fucking Keith in short, hard snaps of his hips, and he really underestimated how worked up he'd gotten Keith, because Keith suddenly turns his face against Shiro's neck and _whines_  and says, "I - I can't - "   
  
"You _can_ ," Shiro says, voice almost a growl, and when he wraps an arm around Keith's chest Keith clutches at it helplessly. "Say it," Shiro demands, and Keith moans and nods, arching his back.   
  
"Yes, sir," he gasps.   
  
"You feel so good, baby," Shiro whispers, and Keith's making little hiccuping gasps every time Shiro fucks into him and Shiro wants to _ruin_  him, "so good, so tight for me - "   
  
Keith's so _wet_ , when Shiro looks, leaking all over himself, but Keith pushes his hand away when Shiro moves to touch him.   
  
"I want to come like this," Keith says, and Shiro smirks and puts his hands back on Keith's hips and shifts, looking for the spot that spills Keith over every time. His legs are starting to ache with the strain of supporting them both but they're both so close, and Keith sobs when Shiro finds his prostate again, writhing in Shiro's grip and gasping, "Please, sir, let me come, let me - "   
  
"Just a little longer, sweetheart, come on," Shiro manages, and Keith cries out, trembling in Shiro's arms, but he holds on and Shiro's so proud of him, because Keith's so good, so good for him, and Shiro finally says, "You've done so well, baby, you can come, come for me," and Keith wails and comes all over himself, completely untouched.   
  
He goes pliant and heavy in Shiro's arms, making soft little cries as Shiro keeps fucking him, oversensitive and overwhelmed, and when Shiro comes Keith moans along with him, gasping and leaning his head back on Shiro's shoulder, one hand finding its way into Shiro's hair and gripping hard to ground himself.   
  
Shiro's not entirely sure he can support them both much longer, his legs trembling as hard as Keith is, and so he lifts Keith as gently as he can and pulls out, both of them wincing. He tries to lay Keith down gently as well, but Keith falls forward of his own volition, pressing himself to the sheets and just breathing, and so Shiro takes a moment to dispose of the condom and fetch Keith a warm cloth.   
  
Keith hasn't moved by the time he comes back, and Shiro nudges him until he acquiesces and moves to lay properly on the bed, letting Shiro pull away the dirty sheets and sit beside him.   
  
"Hey," Shiro says when Keith still doesn't speak, and he rubs his hand over Keith's back, cool with sweat. "You okay?"   
  
"Shiro," Keith mumbles finally, and he makes to crawl into Shiro's lap, but Shiro encourages him onto his back instead. There's a subtle tear track running down Keith's face, and Shiro wipes it away with his thumb.  
  
"There we go," he says, and some other day, he'd clean Keith with his tongue, but Keith looks so fucked-out and exhausted Shiro just runs the cloth over his stomach, wiping gently between his legs and keeping an eye on Keith as Keith watches him in return.   
  
Keith makes an impatient noise when Shiro stands up again. "Will you come here?" he says, and the humour in his tone is reassuring.   
  
"I need to get you the lotion," Shiro says, gesturing - rather impolitely, in hindsight - to Keith's thighs, where Shiro knows the flesh is red and so, _so_  pretty, but still in need of care.   
  
"Do it in a minute," Keith says lazily, and Shiro sighs but lays down next to him anyway, smiling when Keith joins their hands.   
  
"Was that okay for you?" he asks after a moment, because sure, they talk around this all the time, but what if -   
  
"It was amazing, Shiro, like always," Keith reassures.   
  
"The spanking wasn't too - "   
  
" _Shiro_ ," Keith groans, because even after that, even after everything they do together, he still gets curiously, endearingly embarrassed. "It was - I liked it. A lot."   
  
"Okay," Shiro says, and he leans over to kiss Keith's cheek. "Good."

**Author's Note:**

> i deeply apologise for making voltron their safeword but i apologise for nothing else
> 
> please leave a comment if you enjoyed, and subscribe to my profile or this series if you'd like to read more of my sheith month fics!
> 
> you can find me on twitter at twitter.com/starboysheith, and tumblr at starboykeith.tumblr.com !


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